Automated teller machines have been used in financial institutions and such like to carry out transactions with customers, e.g. transactions of depositing cash, namely bills and coins, or withdrawing cash by a customer.
A conventional automated teller machine includes a bill slot for delivering and receiving bills to and from a customer, a validator for determining the denominations and authenticity of bills deposited in the machine, a temporary holding section for temporarily holding deposited bills, and denomination-sorted cassettes for stocking bills sorted by denominations.
In the automated teller machine, when the customer inserts bills into the bill slot of the automated teller machine, the validator distinguishes the deposited bills, and the temporary holding section temporarily storing the bills, when being determined as authentic ones, whereas bills considered as being inappropriate are returned to the bill slot to give them back to the customer. Subsequently in the automated teller machine, the customer fixes the amount of money to be deposited, and the validator in turn determines again the denominations of the bills stored in the temporary holding section to store the bills in the denomination-sorted cassettes according to the denominations thus determined.
There are some types of bills of which certain part is printed with a magnetic ink. In that case, the validator detects the magnetism of the magnetic ink by means of a magnetic sensor to refer to the position and strength of the detected magnetism for determination of the denomination and authenticity of the bill. Japanese patent laid-open publication No. 2010-198337 discloses a bill validating apparatus which includes a validator having the validation function.
In an automated teller machine to which the above bill validating apparatus is applied, the validating section includes guide rollers arranged in the vicinity of a magnetic sensor for conveying bills so as to bring bills into contact with the magnetic sensor. As the guide rollers, use is often made of bearings that are ball bearings of which the substance is selected to metal, particularly magnetic substance, in light of durability, costs and the like.
However, the bearing of magnetic substance may, for instance, become magnetized during assembly work or maintenance work of the validator. In that case, as the guide rollers rotate, the bearings will cause the magnetic field therearound to change. It causes a problem that the magnetic sensor senses the changing magnetic field as noise, leading to the decrease in the accuracy of sensing the magnetism of bills.